rle-compression

Program to compress and extract files using the run-length encoding algorithm.

Important note :

This implementation is a modified version of the algorithm to allow a better compression ratio.

Refer to the Technical specifications section for more information.

Documentation

Supported OS

This software is officially compatible on both Linux and Mac.

Compile from source

Use the following command:

make

Install

make install

Uninstall

make uninstall

Usage

rle [OPTION] SOURCE DEST

Options list:

• -c compress SOURCE to DEST
• -x extract SOURCE to DEST
• --help display help and exit
• --version output version information and exit

Example

To compress the file named foobar.txt, the command will be:

rle -c foobar.txt foobar.rle

Now let's extract this file:

rle -x foobar.rle foobar.old

foobar.old has the same content as foobar.txt.

Technical specifications

Description

The format used during compression is as follows:

[128-255][byte]
# Format of a compressed sequence
# (first byte value - 126) give the compressed sequence length between 2 and 129
# The following byte contain the value

[0-127][byte 0][byte 1]...[byte n]
# Format of a uncompressed sequence
# (first byte value + 1) give the uncompressed sequence length between 1 and 128
# The following n bytes contain the value

Examples

# Exemple 1: "AAAA" which can be reduced to "4A"
[130][A]
# length = 130 - 126 = 4
# byte value = A

# Exemple 2: "ABCDE" which cannot be reduced
[4][A][B][C][D][E]
# length = 4 + 1 = 5
# bytes value = [A, B, C, D, E]

# Exemple 3: "foobar"
[0][f][128][o][2][b][a][r]
# or [1f 2o 1b 1a 1r]

License

This project is licensed under the MIT License - see the LICENSE file for details